Influenza virus is a NIAID "Class C Priority Pathogen" and a significant public health and agricultural problem. Using a combination of genomic technologies and hypothesis-driven molecular approaches, we are studying the evolutionary struggle between influenza virus and the host cell. Our work has demonstrated that influenza virus ensures the efficient translation of its mRNAs by recruiting a cellular protein, P58IPK, to down-regulate the interferon (IFN)-induced protein kinase, PKR. Recently, we found that P58IPK is transcriptionally induced during endoplasmic reticulum stress and interacts with and inhibits PERK, another elF-2 alpha kinase. It thus appears that P58IPK is responsive to multiple stress signals, and through its ability to inhibit elF-2 alpha kinases, plays a central role in regulating protein synthesis and indirectly virus replication. We have recently generated mice that lack the P58IPK gene. These mice, which develop defective pancreatic islets and diabetes, provide an invaluable tool for dissecting the cellular and viral-regulated functions of P58IPK. In Aim 1 we will determine the susceptibility of these mice to infection with wild type or mutant influenza viruses. In Aim 2, we will focus on a molecular and biochemical dissection of the events that occur in influenza virus infected mouse embryo fibroblasts (MEFs) obtained from P58IPK knockout mice and from mice with deletions in the PERK gene or with a "knock-in" mutation resulting in a nonphosphorylatable elF2 alpha subunit. In Aim 3, we will take a functional genomics approach to complement the first two aims and set the stage for future work. We will perform micro-array analyses on RNA prepared from infected MEFs and from tissues obtained from wild type and P58IPK knockout mice infected with wild type or mutant viruses. We will also perform targeted proteomic analyses to identify P58IPK interactive partners using tandem affinity purification, mass spectrometry, and bio-informatic tools for network modeling. Our underlying hypothesis is that influenza ensures its efficient replication by evading host innate and stress defenses through recruitment or activation of cellular genes and proteins such as P58IPK. The identification of host pathways impacted by influenza virus should reveal novel therapeutic targets and lead to improved antiviral therapies and vaccines.